For years, epidemiological and scientific studies have supported a role for solar ultraviolet radiation (UVR) in the development of melanoma. Our new data suggests that UV rays can differentially affect the expression of microRNAs (miRNAs) in the melanocytes of healthy persons versus those who have a history of melanoma. We therefore hypothesize that melanoma prone melanocytes, when exposed to solar UVR, differ markedly from healthy melanocytes in the deregulation of miRNAs and that this aberrancy leads to the perturbation of molecular pathways that contribute in part to the development of melanoma. With the use of novel techniques and proteomic technology, we will test this hypothesis by performing the following studies: Aim 1 - Evaluate the expression of miRNAs between the melanocytes of healthy persons and melanoma patients after exposure to solar UVR in situ. Specifically we will: a) Use biologically relevant doses of simulated solar UVR (ssUVR) to irradiate a statistical number of human volunteers (both healthy and melanoma patients), and thereafter isolate irradiated or un-irradiated melanocytes by laser capture microdissection (LCM). b) Quantify relative changes in the expression of miRNAs between the irradiated and un-irradiated melanocytes from each volunteer and then use bioinformatic approaches to identify miRNAs that are commonly deregulated amongst each of the two groups. c) Confirm the expression patterns observed on the microRNA array cards and use currently available software databases to tentatively predict miRNA target genes. d) Perform parallel experiments to profile mRNAs between the same set of irradiated and un-irradiated melanocytes as a first step in identifying candidate UV-responsive miRNA-mRNA relationships. Aim 2 - Identify proteomic pathways potentially affected by aberrantly expressed UV-responsive miRNAs in melanocytes of melanoma patients. Specifically, we will: a) Use reverse phase protein microarrays (RPMA) to measure the quantity of individual proteins (miRNA targets) between the irradiated and un-irradiated melanocytes of melanoma patients or healthy individuals. b) Use this new class of proteomic profiling technology to analyze the potentially altered state of molecular pathways relevant to the early development of melanoma.